Here is how to print emails in the new mail: https://help.yahoo.com/kb/sln28328.html
Have you printed an email only to find the page includes distracting menus, ads, and buttons? Print a clean hard copy to keep for your records.
1. Open an email you'd like to print.
2. Click More at the bottom.
3. Select Print.
4. Click Print in the popup window.
5. Follow the browser prompts to complete.